US3115688A

US3115688A - Cable clamp

Info

Publication number: US3115688A
Application number: US141789A
Authority: US
Inventors: Karl E Smith
Original assignee: BETHEA CO Inc
Current assignee: BETHEA CO Inc
Priority date: 1961-09-29
Filing date: 1961-09-29
Publication date: 1963-12-31
Anticipated expiration: 1980-12-31

Description

Dec, 31, 1963 K. E. SMITH CABLE CLAMP Filed Sept, 29. 1961 INVENTOR.

57a f A Hffor/zeys United States Patent Dfiice 3,115,688 Patented Dec. 31, 1963 3,115,68S CABLE CLAMP Karl E. Smith, Birmingham, Ala, assignor to Bethea Company, line, a corporation of Alabama Filed Sept. 29, 1961, Ser. No. 141,789 3 Claims. ((11. 24-125) This invention relates to a cable clamp and more particularly to such a clamp which shall be adapted for making electrical and mechanical connections for cables, Wires and the like whereby the required clamping pressure is applied to the cable to promote a good electrical or mechanical joint.

An object of my invention is to provide a combined groove and keeper constricting unit for a cable clamp which shall have increased holding ability, increased mechanical advantage in clamping the cable and at the same time will provide improved means for compensating for the increased unit pressure loadings on the conductor regardless of the size of cable being clamped within a given range of a specific clamp.

A more specific object of my invention is to provide a cable clamp of the character designated in which a uniform pressure is applied to a substantial area of the cable being clamped without applying excessive pressure at specific points along the cable, thereby minimizing initial high unit pressures at such points which would tend to exceed the elastic limit of the cable material and cause excessive cable deformation and strand damage.

Cable clamps embodying features of my invention, as well as cable clamps showing the problems encountered in the use of prior art clamps, are illustrated in the accompanying drawing, forming a part of this application, in which:

FIG. 1 is an end elevational view of the clamp, showing the cable being clamped in section;

FIG. 2 is a vertical sectional view taken generally along the line 22 of FIG. 1;

FIG. 3 is a vertical sectional view of a conventional type clamp which is designed for receiving a large size cable and having a large size cable therein;

FIG. 4 is a vertical sectional view through the clamp shown in FIG. 3, but having a small size cable therein;

FIG. 5 is a vertical sectional view through a conventional type clamp which is designed for receiving a small size cable and having a small size cable therein; and,

FIG. 6 is a vertical sectional view of the clamp shown in FIG. 5, but having a large size cable therein.

Referring now to the drawing for a better understanding of my invention, I show in FIGS. 36 conventional type clamps which have been employed heretofore for clamping cables. In FIGS. 36, the clamp comprises a body portion 1% having a clamping groove 11 therein which provides a bearing surface for the cable or wire indicated at 12. Clamping pressure is exerted against the opposite side of the cable 12 from the groove 11 by a clamping member or keeper 13. The clamping pressure is provided by suitable means, such as a U-bolt or the like which engages a groove 14 provided in the keeper 13 and passes through suitable openings 16 provided in the body portion 10.

There are many instances where the mechanical holding ability of a cable clamp is of prime importance, such as where the clamp is employed in the dead-ending of cables and wires used on transmission lines and the like. Also, strain clamps for transmission conductors require considerable ability to hold the conductor rigidly in place whereby the conductor is prevented from being pulled from the clamp under tensile loadings.

To obtain a greater holding ability, conventional type clamps, such as the clamps shown in FIGS. 3-6, are provided with curved clamping grooves 11 which will constrict the cable as the keeper 13 is forced toward the body portion 10. The keeper 13 is also provided with a matching curved surface 17 which is of a generally convex shape, as shown. Where unusual holding ability is required the clamping groove 11 may contain one or more of these constricting seats.

The means shown in FIGS. 3-6 for constricting the cable 12 can be quite damaging to the cable where the clamp is not designed for use with a particular size cable. That is, the clamps are usually designed to accommodate a range of cable sizes whereby the clamp is more versatile. Where the clamp is thus required to accom modate a range of cable sizes, the usual curved constricting units often fail to provide proper cable clamping pressures. This is especially true where relatively small size cables are being clamped in a clamp which is designed for use with large cables. For example in FIGS. 3 and 4, the clamp 10 is designed to accommodate a large size cable 12. In FIG. 3, the large size cable 12 is being clamped whereby substantially uniform pressure is applied to the cable by the keeper 13 and the groove 11 int the body portion 10. On the other hand, when a relatively small size cable 12 is clamped in the same clamp, as shown in FIG. 4, the keeper 13 does not bear uni formly on the cable but will initially make a point contact as at 18 whereby there is a concentration of pressure at this point. This concentration of pressure pinches the cable, as shown in FIG. 4, whereby there is an initial high unit pressure which exceeds the elastic limit of the material from which the cable is formed, thus causing excessive cable deformation and strand damage.

When the conventional type clamp is designed to accommodate a smaller size cable, as shown in FIGS. 5 and 6, the keeper 13 will again produce concentrated loads on the cable 12 for which the clamp was not designed. That is, where a small size cable 12 is inserted in the clamp shown in FIG. 5 the clamping surface 11 of the body portion 10 and the clamping surface 17 of the keeper 17 are generally parallel to each other whereby a uniform pressure is exerted. On the other hand, where a larger size cable is inserted in the same clamp, as shown in FIG. 6, concentrated pressures or loads are imparted to the cable at points 19 while the portion of the cable intermediate the points 19 is not clamped uniformly, as clearly shown in FIG. 6.

The clamps described hereinabove are conventional type clamps and are illustrated to show the problems which exist at the present time where clamps are required to accommodate a range of cable sizes. My improved cable clamp is shown in FIGS. 1 and 2 and comprises a body portion 20 having a curved clamping groove 21 therein which forms a bearing surface for the cable 12. Cooperating with the opposite side of the cable 12 from the groove 21 is a keeper 22 having a groove 23 therein for receiving a U-bolt 24 or the like. Suitable openings 26 are provided in the body portion 20 for receiving the legs of the U-bolt 24, as shown. The keeper 22 is urged toward the body portion 20 whereby the parts remain in clamping relation by suitable retaining nuts 27. Also, suitable lock washers 28 may be inserted between the retaining nuts 27 and the adjacent surface of the body portion 20, as shown.

The clamping groove 21 is defined by downwardly and inwardly converging side portions and each of the side portions of the groove is provided with a straight line contact surface 29 as viewed in longitudinal section. The contact surface 29 is relatively long, as indicated by the arrows 30. The surface of the keeper 22 facing the clamping groove 21 is also defined by downwardly and inwardly converging side portions which are disposed opposite the downwardly and inwardly converging side portions of the groove 21. Each of the side portions of the keeper 22 are provided with straight line contact surfaces indicated at 31. The contact surfaces 31 are not only directly opposite the contact surfaces 29 but are of substantially the same length and parallel to the contact surfaces 29 whereby a uniform clamping action is obtained throughout the entire length of the clamping surfaces, as indicated by the arrows 30.

As clearly shown in FIG. 2, the distance between the clamping surfaces 29 and the clamping surfaces 31 is less than the distance between the remaining portions of the clamping groove 21 and the keeper 22. That is, the contact surfaces 29 are joined to each other by a curved intermediate portion 32 while the contact surfaces 31 of the keeper are joined to each other by a curved surface 33. By providing the curved surfaces 32 and 33, the cable is free to curve around the keeper during clamping whereby it follows the clamping contour of the keeper. The curved surface 32 is usually struck on a radius equal to or slightly less than the radius on which the curve surface 33 is struck. However, with minimum size conductors, the curved surface 32 may be struck on a radius greater than the radius on which the curved surface 33 is struck so as to provide uniform spacing throughout the clamped area of the smaller conductor, thus providing more clamping area. By providing the greater distance between the curved surfaces 32 and 33 than the distance between the contact surfaces 29 and 31, a clearance is always provided between the surfaces 32 and 33 whereby firm contact is assured between the contact surfaces 29 and 31 at all times. Also, by providing a greater distance between the curved surfaces 32 and 33 than the distance between the contact surfaces 29 and 31, I assure that the contact surfaces 29 and 311 will always assume the bearing load uniformly rather than the curved surfaces 32 and 33. Furthermore, for a given clamping pressure, this feature will tend to compensate for the increased unit pressure encountered as successively smaller diameter cables are clamped.

The angle at which the contact surfaces 29 and 31 are inclined may be varied to accommodate particular design requirements. Also, a pluarlity of the clamping surfaces 29 and 31 may be employed in a single clamp Where more than one clamping groove is provided. Also, the cross sectional shape of the clamp may be varied without departing from my invention.

From the foregoing, it will be seen that I have devised an improved cable clamp which not only has the usual advantages of increased holding ability and increased mechanical advantage in clamping the cable, but also provides means for compensating for the increased unit loadings on the conductor, such as a cable or the like, regardless of the size of the cable being clamped within a given range of a specific clamp.

While I have shown my invention in but one form,

it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof,

and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

l. A cable clamp comprising:

(a) a body portion having a clamping groove therein defined by downwardly and inwardly converging side portions,

([1) each of said downwardly and inwardly converging side portions of said clamping groove having a straight line contact surface disposed to extend longitudinally of the cable to be clamped and connected to each other by a concave intermediate surface,

(0) a keeper member having downwardly and inwardly converging side portions thereon disposed opposite said downwardly and inwardly converging side portions of said groove,

((1) each of said downwardly and inwardly converging side portions on said keeper having a straight line contact surface opposite and parallel to the adjacent straight line contact surface of said clamping groove and being connected to each other by an intermediate convex surface opposite said concave surface,

(e) the distance between opposite straight line contact surfaces between said keeper and said clamping groove being no greater than the distance between other portions of said keeper and said clamping groove,

(f) the convex surface of said keeper member and the concave surface of said clamping groove between the straight line contact surfaces being spaced from each other a distance greater than the distance between the oppositely disposed straight line contact surfaces of said keeper member and said clamping groove, and

(g) means to hold said keeper member and said body portion in clamping relation to each other.

2. A cable clamp as defined in claim 1 in which the clamping groove is generally U-shaped as viewed in transverse cross section.

3. A cable clamp as defined in claim 1 in which the concave surface of said clamping groove is struck on a radius no greater than the radius on which the convex surface of said keeper member is struck.

References t'lited in the file of this patent UNITED STATES PATENTS 478,822 Seward July 12, 1892 1,370,544 Leeper Mar. 8, 1921 1,407,477 Plimpton Feb. 21, 1922 2,196,383 Buchanan Apr. 9, 1940 2,348,100 Wadsworth May 2, 1944 2,884,476 Lock et al. Apr. 28, 1959 FOREIGN PATENTS 526,668 Belgium Mar. 15, 1954

Claims

1. A CABLE CLAMP COMPRISING: (A) A BODY PORTION HAVING A CLAMPING GROOVE THEREIN DEFINED BY DOWNWARDLY AND INWARDLY CONVERGING SIDE PORTIONS, (B) EACH OF SAID DOWNWARDLY AND INWARDLY CONVERGING SIDE PORTIONS OF SAID CLAMPING GROOVE HAVING A STRAIGHT LINE CONTACT SURFACE DISPOSED TO EXTEND LONGITUDINALLY OF THE CABLE TO BE CLAMPED AND CONNECTED TO EACH OTHER BY A CONCAVE INTERMEDIATE SURFACE, (C) A KEEPER MEMBER HAVING DOWNWARDLY AND INWARDLY CONVERGING SIDE PORTIONS THEREON DISPOSED OPPOSITE SAID DOWNWARDLY AND INWARDLY CONVERGING SIDE PORTIONS OF SAID GROOVE, (D) EACH OF SAID DOWNWARDLY AND INWARDLY CONVERGING SIDE PORTIONS ON SAID KEEPER HAVING A STRAIGHT LINE CONTACT SURFACE OPPOSITE AND PARALLEL TO THE ADJACENT STRAIGHT LINE CONTACT SURFACE OF SAID CLAMPING GROOVE AND BEING CONNECTED TO EACH OTHER BY AN INTERMEDIATE CONVEX SURFACE OPPOSITE SAID CONCAVE SURFACE, (E) THE DISTANCE BETWEEN OPPOSITE STRAIGHT LINE CONTACT SURFACES BETWEEN SAID KEEPER AND SAID CLAMPING GROOVE BEING NO GREATER THAN THE DISTANCE BETWEEN OTHER PORTIONS OF SAID KEEPER AND SAID CLAMPING GROOVE, (F) THE CONVEX SURFACE OF SAID KEEPER MEMBER AND THE CONCAVE SURFACE OF SAID CLAMPING GROOVE BETWEEN THE STRAIGHT LINE CONTACT SURFACES BEING SPACED FROM EACH OTHER A DISTANCE GREATER THAN THE DISTANCE BETWEEN THE OPPOSITELY DISPOSED STRAIGHT LINE CONTACT SURFACES OF SAID KEEPER MEMBER AND SAID CLAMPING GROOVE, AND (G) MEANS TO HOLD SAID KEEPER MEMBER AND SAID BODY PORTION IN CLAMPING RELATION TO EACH OTHER.